One of my neighbors and his significant other cruise regularly on Carnival .Yesterday he told me that his SO received an e-mail from Carnival with an offer of $900 to gamble on a future cruise as well as a great cabin and location for a December 2015 cruise .

I have never heard of anything like this before .Is this the norm or is it something rarely done ?

Your gambling level on previous cruises determines what they offer. It could be 25% off all the way to a free cruise. Never heard of free money to cruise but if they typically loose 5k on a cruise why not?